This disclosure relates generally to a control system and method for controlling the flow of oil and gas from a well bore casing to a production tubing and, more particularly, to such a system and method utilizing a plurality of valves for controlling the oil and gas flow.
In oil production installations, a well bore annulus, or casing, lines the well bore. Oil and gas (hereinafter "production fluid") present in an underground oil reservoir flows into the casing through perforations in the casing. Production tubing for transporting the production fluid from the reservoir level is disposed in the casing and extends upwards to the ground surface.
A valve is often used to control production fluid flow from inside the casing to the production tubing. One type of conventional valve uses a sliding sleeve valve, or choke, that utilizes a slotted sleeve which axially slides over a slotted port. However, a single choke valve does not allow for any incremental control of the production fluid flow. Furthermore, the linearly sliding choke occupies a relatively large space, which can be a major disadvantage since the casing interiors are relatively narrow, thus requiring greater valve lengths, and thus more material to manufacture the valve.
Another valve design uses an electro-hydraulic control system to open or close a valve, and a solenoid to control a hydraulic line. However, this design also does not allow for incremental production fluid flow control, utilizes a relatively large amount of electrical power, and is also relatively bulky.
Therefore, what is needed is a system of the above type that provides incremental control over the fluid flow, yet is simple, inexpensive, and relatively small in size.